bump default max_concurrent_requests to 500, update config comment

also raise 1024 bytes to 4096 bytes in minimum max_request_size check

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/config/mod.rs

@@ -402,7 +402,7 @@ fn default_max_request_size() -> u32 {
 }
 
 fn default_max_concurrent_requests() -> u16 {
-    100
+    500
 }
 
 fn default_max_fetch_prev_events() -> u16 {